You do not need to spend money to win the cup, its not that difficult, with decent tactic and attending at every cup game .... it should be doable.....
I have won cup 7 times and even if "sleepers" (managers who sleep few seasons and than buy decent players at their level) are not a problem....
make sure that all your players are NGE so wake up early and buy them, not rubbish who has been sold during the day
always give your player special ability , although its not confirmed, I do believe, special ability can rate as a 1 star, at least it looks that way from my games...
here you go some results I did this season... QF Attachment 72941
, second I have won 3-2 at home
today, another sleeper turned up ... and left with empty hands... cant wait for replay game
and one more thing I forgot to mention... in the games you play stronger opponent, NEVER make a sub (as per images, I do not do it anymore.... everytime I did a sub, I conceded badly..... I think its a bug (not confirmed haha, but works for me )
Just never give up, never spend money and use right tactic, you will do it one day mate Attachment 72938